Light sensor with optical light piping

ABSTRACT

An adjustable mount adapted to selectively align exit faces of a plurality of optical fibers with a transducer to enable remote readout of light intensity at the entrant face of each fiber.

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[72] lnvcntor Rudolf Hartmann References Cied SkokieJll. U ED STATESPATENTS 1 1 pp 780,095 2.938.666 5/1960 Rand....... 250/227x I 1 Filed1968 3.114.283 12/1963 Gruner 250/227x H Pflwmed 3 3.372.240 3/1968Boyerset al. 250/227x I 1 Asslgnee Cmnlmy 3.407.304 l0/l968 Kinard etal. 250/227x chlcagm 3.436.757 4/1969 Schwab 250/227x 3.483.389 12 1969Cronin 250 227x Primary Examiner-Roy Lake [54] LIGHT SENSOR WITH OPTICALLIGHT PIPING Assistant EraminerC. R. Campbell 16 Claims, 3 Drawing Figs.Attorney-William F. Pinsak [52} U.S- CI 250/220,

250/227. 250/237 [51 Int. Cl G02b 5/16, ABSTRACT: An adjustable mountadapted to selectively align 1 HOlj 39/1 2 exit faces of a plurality ofOptical fibers with a transducer to [50] Field of Search 250/227. enableremote readout of light intensity at the entrant face of ounnun nuulvleach fiber.

PATENTEUJANZBISYI 35581395 3 1720671157.- 5 56 a2 Rudolf flarzmann. an

52 By W LIGHT SENSOR WITH OPTICAL LIGHT PIPING The present inventionrelates to light sensing. Particularly, the invention relates toapparatus for sensing light from a plurality ofsmall stations.

Measurement of incident light at small stations such as those found inapertures in cameras, projectors and film printers conventionally hasbeen attended with problems arising from difficulty of accessibility.Space limitations within such devices prevent accurate positioning ofheretofore known photodetectors (light detectors) while scanning of anaperture for measurements at a plurality of stations has beenpractically impossible because known scanning mechanisms are larger thanphotodetectors.

The nature of the problem is perhaps more readily appreciated byconsidering a conventional film printer. In such a device. raw filmstock is exposed. frame by frame, to modulated light passed through anoriginal developed negative to produce a printed film. The modulation ofthe light is intended to normalize lighting in the pn'nted film byovercoming the effect of undesired variation in hue and intensitypresented in the negative. The station in the printer at which the lightis passed from its source through the negative is its aperture, and anexceedingly small opening, approximating the size of a film frame. Toproduce proper light effects in the finished product, it is requiredthat the quantity of light at all positions in the aperture be uniformfor each frame, as variations would tend to defeat the purpose of thenormalizing process intended to be effected by the printer.

An object of the present invention is to detect and measure light atsmall conventionally inaccessible stations.

Another object of the invention is to measure light from any selected ofa plurality of small stations at which light is simultaneously detected.

A further object of the invention is to utilize light energy, forexample, to determine its intensity remotely from a station at which thelight is detected.

The foregoing objects are effected in accordance with the presentinvention by providing a sensor for light which comprises a plurality ofoptical fibers. Each fiber has an entrant face arranged for lightreception from an associated station and an exit face for output oflight from such station. Means including a light transducer disposedremote from the light stations enable utilization of fiber transmittedlight. Means are provided for selectively aligning e'ach exit face withthe light transducer to the end that the light transmitted by an fibercan be utilized.

In accordance with one feature of the invention the entrant faces of thefibers are mounted in uniformly spaced relationship in a holder which isadapted to be positioned in a light aperture, such as the aperture in afilm printer. Accordingly, light intensity at uniformly separatedpositions or stations within the aperture can be compared by'readout onthe utilizing device, such as a photometer.

Another feature of the invention enables separation of light from eachstation into its various color components for determining the intensitythereof. In consequence, the quality of the light at each station aswell as its quantity can be determined remotely from the sensingstations.

Further and other objects will be apparent from the description of theaccompanying drawings in which like numerals refer to like parts.

In the drawings:

FIG. I is a perspective view of apparatus embodying the presentinvention, with parts broken away for illustration;

FIG. 2 is a sectional view taken along the line 2-2 of HG. l; and

FIG. 3 is a sectional view taken along the line 3-3 of HO. 2.

Referring now more particularly to the drawings, a sensor, generallydesignated 10, for light at a plurality of stations (not shown)comprises a wrapped bundle 12 of optical fibers 14 (only some of whichand their components have been numbcred). Each of said fibers has aninput end portion 18 with an entrant face 19 (FIG. 1) arranged for lightreception from and an output end portion 16 with an exit face 17 (FIG.2) arranged for light output from, a respective of said stations. Thesestations may be relatively widely spaced apart from each other or closetogether, such as, for example, in the aperture ofthe aperture plate ofafilm printer for which the exemplary device is adapted. However, ifwidely spaced from one another, then holder 20, hereinafter to bedescribed. may be omitted.

Each of the optical fibers is shown as being enclosed in a sheath 28 ofconventional plastic composition which terminates short of itsassociated exit and entrant faces 17 and 19. These sheaths projectoutwardly from opposed input and output end portions 30 and 34 of thecover defining bundle 12 about fiber end portions l6 and 18 and therebyenable an optional arrangement of the entrant and exit faces of thefibers.

Holder 20, which may be a suitable plastic or hard clastomericcomposition such as silicon rubber. comprises holding means in whichinput end portions 18 are potted to hold entrant faces 19 inpredetermined relative spaced-apart disposition. In the presentembodiment, the entrant faces are uniformly spaced one from the other ona light proximate face of an adapter or key 32 which is fashionedintegrally with the holder and may be proportioned for reception in alight passing aperture. This enables sampling of the light intensity atpositions in such aperture corresponding to entrant faces 19.

A mount 26 means for selectively associating each cxit face with a lighttransducer 24 for light utilization. For that purpose, said mount has anelongated body from the top ofwhich the bundle 12 extends upwardly andin which output end portions 16 of the fibers are rigidly secured.lfdesired, the mount may be fabricated from any suitable plastic or hardelastomeric material such as silicon rubber, in which the fibers arepotted to hold exit faces 17 in predetermined positions, preferable forprojection of light vertically downwardly. Herein said exit faces arespaced apart in linear alignment longitudinally of said mount.Transducer 24 is included in means generally designated 22 for utilizingfiber transmitted light, and is disposed remote from entrant faces [9.Said transducer may be of any known construction, such as is embodied ina generative, photoresistive, photomultiplier, or phototube-photodetector. The details of construction of the transducer are notcritical to the invention, its function being to convert the photonoutput from exit faces into electrons.

Utilizing means 22 also includes a device 36 for using the electronoutput of transducer 24. Exemplary device 36 is an amplifier-photometerwhich is operatively connected through circuit 38 with transducer 24 tothe end that the current generated by said transducer will causemovement of a photometer indicator 40 enabling readout on scale 41 ofintensity of light emitted from any of selected faces 17. The details ofconstruction of the amplifier-photometer are not limiting on theinvention, and accordingly, further description is omitted.

Light collimating lens or element 42 is arranged to pass light from aselected exit face 17 toward transducer 24. For that purpose, the lensis mounted in the end of tube 44 which may be fashioned integrally andproject upwardly from base 46 for holding the lens in optical alignmentwith, and in spaced-apart relationship from, said transducer.

An elongated stand 48, which has the shape of an inverted U" in crosssection, comprises track means with an upper medial section or track 49which is supported from the base above lens 42. Said track has a slot 50which extends longitudinally of the alignment of faces 17 in mount 26.The lower end portion of said mount is restricted to form an elongatedspline or slide 52 which is disposed in the slot 50 and proportioned toenable the mount to move longitudinally of track 49 to selectively alignthe exit faces with transducer 24. Movement ofslide 52 is facilitated bya pair of bearing shoulders 54 and 58 which are fast with said mount andarranged on opposite side of slot 50in sliding engagement with the uppersurface of the track 49.

Exit faces 17 herein are shown as terminating at the lower faces 57 ofslide 52. Attenuating means comprised of a plate 56 forms a cover overthe lower face of slide 52 on which said plate is secured. Plate 56 isproportioned for extension beyond the sides of slot 50 and is disposedin bearing engagement with the underside of track 49. Thereby, saidplate functions to hold mount 26 in said track by preventing its upwardremoval.

Plate 56 has a light passing aperture 60 (only some of which arenumbered) extending vertically thcrethrough in alignment with each exitface 17. The diameter ofeach aperture preferable is greater than thediameter of its' associated exit face. An attenuator 62 which hereincomprises a neutral density discshaped filter is disposed in eachaperture 60 normal to the path of light emitted from, and over anassociated exit face. The attenuators are adapted to normalize lightoutput differcnces from exit faces 17 resulting from variation intransmittance characteristics of fibers 14.

The spacing of exit faces 17 longitudinally of mount 26 is such thatonly one fiber at a time can be optically aligned with the lens 42, tothe end that selective alignment of exit faces with transducer 24 ismost effective. To prevent misalignment of the mount with lens 42,shoulder 58 is fashioned as an indexing member, that is, a rack bar witha plurality of external aligned notches 64 spaced longitudinally ofmount 26. A detent 66 urged toward mount 26, is-carried from one end ofa spring arm 68 which has an opposite end adjustable secured to thestand 48. The detent is fashioned for mount holding engagement in anyselected of notches 64 and disengagement therefrom upon application ofmanual force to move the mount in either longitudinal direction.

The apparatus aforedescribed comprises complete means for remotelymeasuring the intensity of light from a plurality of stations. However,such apparatus can be further adapted for measuring the quality of thelight from each station. In the illustrated apparatus, this is achievedthrough the agency of filter means generally designated 70 andcomprising a turret in the form ofa disc 72 which is constrained in ahorizontal plane for rotation with a vertical spindle 76. The latter isjournaled in a bearing sleeve 74 which projects upwardly from base 46 asan integral extension and may be interruptible power driven by anysuitable means 78.

Disc 72 has a plurality of apertures 83 which project verticallytherethrough and preferable are equally angularly spaced, one fromanother, at a uniform radial distance from the center of disc rotation.Color elements or filters 79, 80 and til each adapted for passing lightof a different primary color,

are mounted respectively in three of the apertures 83. A plain elementor glass 82 for passing while light unaffectedly is mounted in a fourthof the apertures 83. The horizontal level of disc 72 is below track 49;and said discis proportioned and arranged to enable each aperture 83 tobe aligned between,

plate 56 and lens 42, permitting any selected aperture to be verticallyaligned with any selected exit face 17 and the transducer 24. Inconsequence of the foregoing, the intensity-of various hue factors oflight at any sensed station can be determined.

Exemplary indexing means for suitably aligning a selected of theelements 79, 80, 81 and 82 in operative position comprises a detent 84spring-urged toward disc 72, which is carried on the end of spring arm86, suitable supported from base 46. The detent is fashioned forengagement in selected of a plurality of outwardly opening notches 88formed in the circumference of disc 72, and for disengagement from suchnotches upon manual application of torque to move said disc in eitherangular direction.

Transducer 24 may not have the same level of sensitivity to all hues.Compensation for such variation in spectral sensitivity may be throughthe agency of neutral density filters, of which as few as one may beused ifsufficient for the normalizing requirement. Herein, exemplaryneutral density filters 90 and 92 are shown arranged in the light pathsthrough elements 80 and 82, respectively, and mounted adjacent thereto.By

reason of the foregoing, accurate remote measurement .of

both quantity and quality of light in heretofore practically inaccessible places can be achieved with relative ease.

lclaim: t

l. A sensor for light at a plurality of stations comprising:

a plurality of optical fibers, each having an entrant facc arranged forlight reception, and an exit fact for output received by its entrantface from a respective station:

attenuating means disposed over said exit faces for normalizing lightoutput differences resulting from variation in light transmittancecharacteristics of said fibers;

means including a light transducerassociated with said exit faces forutilizing fiber transmitted normalized light; and

means for selectively aligning each exit face with said lighttransducer.

' 2. A combination according to claim 1 in which said aligning meanscomprises a mount arranged for adjustment relative said transducer, saidexit faces carried by said mount for selective alignment with saidtransducer as said mount is adjusted.

3. A combination according to claim 2 further comprising a base, and amember supported from said base and spaced from said mount for passinglight from said exit faces toward said transducer.

4. A combination according to claim 3 in which said cxit faces arespaced apart in alignment remote from said entrant faces and furthercomprising track means supported from said base for guiding said mountover said member.

5. A combination according to claim 2 further comprising indexing meanscarried from said mount for effecting alignment of said exit faces withsaid transducer.

6. A combination according to claim 5 in which said indexing meansincludes a rack carried from said mount and a pawl urged for engagementwith said rack to releasably hold said mount.

7. A combination according to claim 1 in which said attenuating meanscomprises a light attenuator fixed to said mount over each exit face.

8. A combination according to claim 3 in which said member comprises alight collimating lens arranged to pass light from said exit faces, saidtransducer comprising a photodectector fixed relative said base forconverting the photon output passed by said lens into electrons.

9. A combination according to claim 1 further comprising a holder bywhich said entrant faces are mounted.

10. A combination according to claim 9 in which said entrant faces areuniformly disposed.

11. A combination according to claim 9 in which said holder has anadapter fashioned for reception in a lightpassing aperture to enablesampling the quantity of light at positions in said aperturecorresponding to said entrant faces.

12. A sensor for light at a plurality of stations comprising:

a plurality of optical fibers, each having an entrant face arranged forlight reception, and an exit face for output of light received by itsentrant face from a respective of said stations;

means including a light transducer associated with said exit faces forutilizing fiber transmitted light;

means for selectively aligning each exit face with said lighttransducer; and

filter means disposed adjacent said aligning means for passing light ofpredetermined hues toward said transducer from said exit faces.

13. A combination according to claim 12 in which said filter meanscomprises a turret with a plurality of color filters ar ranged forselective disposition between aligned said exit faces and saidtransducer.

, ing detent means for releasably holding said disc is in selectedangular positions.

1. A sensor for light at a plurality of stations comprising: a pluralityof optical fibers, each having an entrant face arranged for lightreception, and an exit fact for output received by its entrant face froma respective station: attenuating means disposed over said exit facesfor normalizing light output differences resulting from variation inlight transmittance characteristics of said fibers; means including alight transducer associated with said exit faces for utilizing fibertransmitted normalized light; and means for selectively aligning eachexit face with said light transducer.
 2. A combination according toclaim 1 in which said aligning means comprises a mount arranged foradjustment relative said transducer, said exit faces carried by saidmount for selective alignment with said transducer as said mount isadjusted.
 3. A combination according to claim 2 further comprising abase, and a member supported from said base and spaced from said mountfor passing light from said exit faces toward said transducer.
 4. Acombination according to claim 3 in which said exit faces are spacedapart in alignment remote from said entrant faces and further comprisingtrack means supported from said base for guiding said mount over saidmember.
 5. A combination according to claim 2 further comprisingindexing means carried from said mount for effecting alignment of saidexit faces with said transducer.
 6. A combination according to claim 5in which said indexing means includes a rack carried from said mount anda pawl urged for engagement with said rack to releasably hold saidmount.
 7. A combination according to claim 1 in which said attenuatingmeans comprises a light attenuator fixed to said mount over each exitface.
 8. A combination according to claim 3 in which said membercomprises a light collimating lens arranged to pass light from said exitfaces, said transducer comprising a photodectector fixed relative saidbase for converting the photon output passed by said lens intoelectrons.
 9. A combination according to claim 1 further comprising aholder by which said entrant faces are mounted.
 10. A combinationaccording to claim 9 in which said entrant faces are uniformly disposed.11. A combination according to claim 9 in which said holder has anadapter fashioned for reception in a light-passing aperture to enablesampling the quantity of light at positions in said aperturecorresponding to said entRant faces.
 12. A sensor for light at aplurality of stations comprising: a plurality of optical fibers, eachhaving an entrant face arranged for light reception, and an exit facefor output of light received by its entrant face from a respective ofsaid stations; means including a light transducer associated with saidexit faces for utilizing fiber transmitted light; means for selectivelyaligning each exit face with said light transducer; and filter meansdisposed adjacent said aligning means for passing light of predeterminedhues toward said transducer from said exit faces.
 13. A combinationaccording to claim 12 in which said filter means comprises a turret witha plurality of color filters arranged for selective disposition betweenaligned said exit faces and said transducer.
 14. A combination accordingto claim 13 in which said filter means includes a neutral density filterarranged in optical alignment with at least one color filter foradjusting the intensity of colored light according to variation inspectral sensitivity of said transducer.
 15. A combination according toclaim 13 in which said turret is fashioned as a rotatable disc with anouter notched edge for selectively indexing said color filters inalignment with said transducer and a selected exit face.
 16. Acombination according to claim 15 further comprising detent means forreleasably holding said disc is in selected angular positions.